Suddenly my car is using lots of gas.  Expensive.  Sometimes its fines for a few seconds.  
Airflow meter is checked and is good.
Fuel pressure is correct.
Pressure regulator is working correctly.  

Any suggestions?

It feels like choking of gas.  
Also the idling is bad for nearly a year, stalling often, ever since I changed the O2 sensor, that is single wired.  

Some of you may know something.
Regards, Zoltan